Regulating transformer tap-changer switch

ABSTRACT

A transfer switch wherein the conventional linkages for operating the movable main contacts and the movable auxiliary contacts are replaced by specific cam means for operating said contacts.

United States Patent [72] Inventors Alexander Bleibtreu;

[51] Int. 1101b 19/56 Anton Schunda; Max Poppl, all of [50] Field ofSearch.......................... 200/11 TC, Regensburg, Germany 1 8 200/11TCX 200/11 TC 200/ 1 1 TC 200/11 TC X S m mm m m N n m E m mmm m P s :2 33

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o e MJJM&RJGP 0 de mm mw m m flm n AFPA P 11:11 1.11] 253 23 2247 333 [1.1.1 [[1 ABSTRACT: A transfer switch wherein the conventional link- [54] REGULATING TRANSFORMER TAP-CHANGER SWITCH ts and the movable by specific cam means for ages for operating the movable main contac auxiliary contacts are replaced operating said contacts.

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sum 6 BF 6 P76 9 F7610 F76 WWW z-wro/Ps: WW 4mm v Q21 WW m m REGULATING TRANSFORMER TAP-CHANGER SWITCH BACKGROUND OF THE INVENTION Tap-changing regulating transformers, and more particularly such transformers known as Jansen-type transformers, include three units, namely a transformer proper having a tapped winding, a selector switch and a transfer switch.

The coaction of these three units is amply described in prior art patents such as, for instance, U.S. Pat. No. 3,174,097, to A. Bleibtreu, Mar. 16, 1965, for TRANSFER SWITCH FOR TAP-CHANGING REGULATING TRANSFORMERS and U.S. Pat. No. 3,218,400, to A. Bleibtreu, Nov. 16, 1965, for TRANSFER SWITCHES FOR TAP-CHANGING REGU- LATING TRANSFORMERS HAVING SQUIRREL-CAGE- SHAPED SUPPORT FOR THE FIXED CONTACTS THEREOF. Reference may be had to these patents as to the way in which the aforementioned three units of a Jansen-type tap-changing regulating transformer coact.

The prior art transfer switches shown in the above patents are provided with linkages for operating the movable contacts thereof. Linkage-type operating mechanisms for the movable contacts of transfer switches are now generally accepted and applied in most instances. It is one object of this invention to provide transfer switches having a more desirable kind of operating mechanism for the movable contacts thereof than the linkages shown in the two aforementioned patents, and more particularly to provide polyphase transfer switches or three-phasetransfer switches having extremely simple operating mechanisms with greatly improved performance characteristics.

The present invention may be viewed as an improvement of the type of transfer switches disclosed in U.S. Pat. 2,833,873, to B. Jansen, May 6, 1958, for MULTI-POLE TAP SWITCH CONSTRUCTION FOR CHANGING TRANSFORMER TAPS UNDER LOAD. The gear operating mechanism for the movable contacts shown in Jansen is, however, less desirable than a linkage operating mechanism for the movable contacts as shown in the two aforementioned U.S. Pats. to Bleibtreu.

Other objects of the invention are to provide transfer switches for tap-changing regulating transformers which make it possible to readily control the time travel characteristic of the movable contacts and hence the velocity of the movable contacts at any point of time during opening and closing of cooperating movable and fixed contacts. This, in turn, makes it possible to optimize the switching process.

It is very often desirable to surround cooperating contacts with an arc chute structure to speed deionization of the products of arcing and to prevent the products of arcing generated by one are to contaminate the gap formed between another pair of cooperating separated movable and fixed contacts. Some prior art operating mechanisms for the movable contacts of transfer switches do not allow the provision of arc chutes, or equivalent arc enclosing devices. It is, therefore, another object of this invention to provide transfer switches for tap-changing regulating transformers. having operating means for the movable contacts which allow the provision of arc chutes, or like are enclosing devices.

SUMMARY OF THE INVENTION A transfer switch embodying this invention includes a plurality of fixed contacts arranged in a sector-of-a-circle pattern. It further includes a plurality of movable contacts each movable into and out of engagement with one of said plurality of fixed contacts. A fixed guide structure guides said plurality of movable contacts along radial trajectories each extending from the center of said sector-of-a-circle pattern toward one of said plurality of fixed contacts. The aforementioned plurality of movable contacts is operated by a movable contactoperating member having a substantially straight center guide means arranged in the median plane of said contact-operating member and cooperating with a fixed fulcrum means allowing said contact-operating member to pivot about said fixed fulcrum means and to move simultaneously radially relative the center of said sector-of-a-circle pattern. The aforementioned contact-operating member is further provided with a pair of lateral arcuate guide means arranged to opposite sides of said center guide means thereof. A plurality of operating pin means each operatively related to one of said plurality of movable contacts and each under the control of one of said pair of lateral arcuate guide means impart motions of said contact-operating member to said plurality of movable contacts. A pivotable drive shaft for said contact-operating member is arranged in the center of said sector-of-a-circle pattern at right angles to a plane defined by said plurality of fixed contacts. Spring means bias said contact-operating member radially outwardly away from said drive shaft. The transfer switch further includes torque-transmitting means for transmitting torques from said drive shaft to said contact-operating member, said torque-transmitting means being adapted to allow radial movements of said contact-operating member relative to said drive shaft.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section of a transfer switch embodying the present invention taken along l-I of FIG. 2;

FIG. 2 shows in the upper left sector Ila-Ila thereof a horizontal section taken along Ila-Ila of FIG. 1, in the right sector II-II thereof a top plan view as seen in the direction of the arrow II of FIG. 1, and in the lower left sector IIb-Ilb thereof a section IIbIIb of FIG. 1;

FIG. 3 is an isometric view of a detail of the structure of FIGS. 1 and 2 showing more particularly the hollow drive shaft of that structure, and the parts arranged immediately adjacent t0 and cooperating with, its hollow drive shaft;

FIG. 4 is aside view of a detail of the structure of FIGS. 1 and 2 showing more particularly its current-carrying contacts and their support;

FIGS. 5-8 show sequential phases of a transfer switching operation as seen in sections along A-B of FIG. 1; and

FIGS. 9-15 show likewise sequential phases of a transfer switching operation in a more detailed and more diagrammatic fashion than FIGS. 5-8.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawings, numeral 10 has been applied to indicate a hollow, or tubular, cylindrically shaped fixed contact support of electric insulating material. Contact support 10 encloses, or bounds, a cylindrical space encompassing 360 degrees. This space may be subdivided by three imaginary radially outwardly extending planes P into three subspaces each encompassing Each of the aforementioned subspaces accommodates the switching means for one phase of a three-phase circuit. Contact support 10 supports a plurality of pairs of fixed contacts of which each pair is arranged along a generatrix of contact support 10. Four pairs of fixed contacts l1,11;l2,l2;13,13 and 14,14 are arranged in each of the aforementioned subspaces encompassing 120. Two pairs of switchover contacts, or auxiliary contacts, 12,12 and 13,13 are arranged between two pairs of main contacts 11,11 and 14,14. Contact studs 15 project transversely through contact support 10. The radially inner ends of contact studs 15 support contacts l1,12,13,14 and are conductively connected with the aforementioned contacts. The radially outer ends of contact studs 15 are conductively connected to flexible conductors or braids 16. The ends of flexible conductors or braids 16 remote from contact studs 15 are conductively connected to terminals 17. The terminals 17 conductively connected to the main contacts 11,11 and 14,14 are intended to be conductively connected to a selector switch, and the terminals 17 conductively connected to the auxiliary contacts .12,l2;13,13 are intended to be conductively connected to switchover resistors W as shown in FIG. 9, in which the aforementioned selector switch has been deleted. A pair of movable main contacts 21,21 is arranged to engage the pair of fixed main contacts 11,11 and to be disengaged from the latter, and a pair of movable main contacts 24,24 is arranged to engage the pair of fixed main contacts 14,14 and to be disengaged from the latter. Similarly a pair of movable auxiliary contacts 22,22 is arranged to engage the pair of fixed auxiliary contacts 12,12 and to be disengaged from the latter, and a pair of movable auxiliary contacts 23,23 is arranged to engage the pair of fixed auxiliary contacts 13,13 and to be disengaged from the latter. Each pair of movable main contacts 21,21 and 24,24 and each pair of movable auxiliary contacts 22,22 and 23,23 is supported by a common contact support 25. Reference character 27 has been applied to indicate a pair of axially spaced parallel guide plates of insulating material of which each is provided with radially extending slots 26. The upper ends of contact supports engage the slots 26 in upper guide plate 27, and the lower ends of contact supports 25 engage the slots 26 in lower guide plate 27. Hence contact supports 25 and all pairs of movable contacts 21,21;22,22;23,23 and 24,24 are guided by the pair of guide plates 27, thus confining the trajectories of these contacts to radii of contact support 10. In FIG. 2 reference numeral 28 has been applied to indicate three tie rods extending parallel to the axis of cylindrical contact support 10, being angularly displaced 120 relative to each other and tying the upper guide plate 27 to the lower guide plate 27. Guide plates 27 are arranged at right angles to hollow drive shaft 29. Hollow drive shaft 29 is arranged in the center of cylindrical contact support 10 and arranged in bearing means which, in turn, are supported by the pair of guide plates 27,27 adjacent the centers thereof. A drive shaft 33 for the selector switch (not shown in FIGS. 1 and 2) operatively related to the transfer switch of FIGS. 1 and 2 is arranged inside of hollow shaft 29. I-Iollow shaft 29 supports a drive spider including sleeve 30 jointly pivotable with shaft 29 and arms 31 integral with sleeve 30 extending radially outwardly from sleeve 30 and defining slotlike apertures 32.

Cooperating pairs of contacts 11,11;21,21 and 12,12;22,22 and 13,13;23,23 and 14,l4;24,24 are arranged in arc chutes 34 of which but one has been shown in FIGS. 1 and 2.

The transfer switch of FIGS. 1 and 2 further includes three movable contact-operating members or segments 35 of which each is provided for operating the movable contacts 21,21;22,22;23,23;24,24 of one of the three phases. The three contact-operating members or segments 35 are arranged within a space bounded by the pair of guide plates 27,27 or, in other words, contact-operating segments 35 are arranged between the pair of guide plates 27,27. Each contact operating segment 35 is provided with two lateral arcuate guide means or slots 36,36 and with a median substantially straight guide means or slot 37 arranged between the arcuate slots 36,36. Three axially extending rods or pins 39 of which each projects through one contact-operating segment 35 pivot each of three slide members, or spring supports 38 to one of the contact-operating segments 35. Spring supports 38 are substantially U-shaped and their flange portions engage the slotlike apertures 32 defined by arms 31 of sleeve 30. Compression springs 40 tend to move slide members, or spring supports 38 radially outwardly and thus tend to move contact operating segments 35 radially outwardly. To this end springs 40 are interposed between sleeve 30 and the web portions of slide members, or spring supports 38. Reference character 41 has been applied to indicate units each including an axially extending stud surrounded by a tubular member rotatably mounted upon it. The studs of units 41 are affixed to the aforementioned contact supports 25 of the pairs of movable contacts 21,21;22,22;23,23;24,24 and the tubular members of units 41 engage the lateral arcuate guide means, or slots 36 provided in operating segments 35.

A fixed fulcrum means or stud 42 cooperates with each straight guide means, or slot 37 in each contact-operating member 35. Studs 42 project transversely through each median straight slot 37 in each of the contact-operating segments 35, allowing a combined pivotal and sliding motion of each contact-operating segment 35 relative to the fixed stud 42 projecting through its median straight slot 37. The upper and the lower ends of each of the studs 42 are secured to, and supported by, a structure 43 of insulating material affixed to the upper guide plate 27 and to the lower guide plate 27, respectively. The structure 43 of insulating material projects radially outwardly through an opening provided for that purpose in cylindrical contact support 10. Reference numeral 45 has been applied to indicate terminals supported by the radially outer portion of insulating structure 43. Ribbon-type conductors, or braids 46 connect terminals 45 conductively with conductive rails, or bars 44 supported by insulating structure 43. If the transfer switch of FIGS. 1 and 2 is operatively related to a Y-connected three-phase transformer terminals 45 form the neutral point of the transformer. This has been more clearly illustrated in FIG. 9. The left portion of FIG. 1 shows how the terminals 45 are conductively connected to conductive rails, or bars 44 by means of ribbon-type conductors, or braids 46. The contact supports 25 of the movable main contacts 21,21;24,24 and the movable auxiliary contacts 22,22;23,23 are conductively interconnected by means of flexible braids 48 and are conductively connected to Y-terminals 45 by means of flexible braids 47, as clearly shown on the right of FIG. 2.

Each movable contact-operating member, or contactoperating segment 35 supports a pair of bellcrank-shaped current-carrying contacts 51 which are pivotable about pins 52 supported by segments 35 and which are under the action of helical springs 53. The term current-carrying contacts as used in this context is applied in reference to contacts specifically designed for current-carrying duty rather than for switching and arcing duty. The arrangement of parts 35,51,52 and 53 is clearly shown in FIGS. 2 and 4. It is apparent from FIG. 4 that each contact-operating member 35 pivotally supports four movable current-carrying contacts arranged in pairs on opposite sides of member 35. Pivots 52 are arranged at points situated between the arms of bellcrank-shaped contacts 51. Springs 53 bias contacts 51 arranged to opposite sides of the median planes of members 35 in opposite directions, as clearly apparent from FIG. 2. Reference character 54 has been applied to indicate stops, or dogs, supported by members 35 limiting the pivotal motions of current-carrying contacts 51 relative to members 35. The movable current-carrying contacts 51 are arranged to engage with, and to part from, fixed current-carrying contacts 55 which are supported by cylindrical contact support 10 of insulating material.

At the beginning of each operation of the transfer switch one pair of movable current-carrying contact 51 on one side of each contact-operating segment 35 parts from its cooperating pair of fixed current-carrying contact 55, and at the end of each operation of the transfer switch the other pair of movable current-carrying contacts 51 on the other side of each contact-operating segment 35 engages its cooperating fixed current-carrying contacts 55. The fixed current-carrying contacts 55 have contact surfaces that are slanted in such a way that the pressure exerted by the contact surfaces of their cooperating movable current-carrying contacts 51 is substantially at right angles to the contact surfaces of the former. This can best be seen in FIGS. 5 and 8. Because of this arrangement of the contact resistance and the voltage drop between contacts 51,55 can be minimized, and the same is true in regard to the pressure of springs 53 required to cause engagement under pressure of current-carrying contacts 51,55.

As is apparent from the above, the arms of contacts 51 to one side of pins, or fulcrum means 52 cooperate with fixed current-carrying contacts 55, and the arms on the other side of pins, or fulcrum means 52 are acted upon by helical contactbiasing spring 53. Flexible braids 56 conductively connected to the last-mentioned arms of current-carrying contacts 51 conductively connect contacts 51 with the pair of movable main contacts 21,21 and 24,24, respectively, situated immediately adjacent thereto. Each pair of fixed current-carrying contacts 55 is conductively connected by means of a bar conductor 57 to the pair of fixed main contacts 11,11 and 14,14, respectively, situated immediately adjacent thereto.

FIGS. 9-15 show diagrammatically sequential steps involved in a transfer switch operation, and FIGS. 5-8 show how these steps are carried out by a mechanism as shown in FIGS. 1 and 2 and described in connection with these figures.

FIGS. 9-15 refer to one single phase of a three-phase transfer switch or, in other words, to one of the three switch sectors shown in FIGS. 1 and 2. A transformer winding Tr has a great number of taps of which but two taps A and B are shown in FIGS. 9-15. In these figures the conventional selector switch has been deleted and tap A shown as being directly conductively connected with fixed current-carrying contact 55 and with fixed main contact 11. Tap B is directly conductively connected with fixed current-carrying contact 55 and with fixed main contact 14. Tap A is conductively connected by the intermediary of a resistor W with fixed auxiliary contact 12, and tap B is conductively connected by the intermediary of another resistor W with fixed auxiliary contact 13. Each of the pairs of fixed current-carrying contacts 55 cooperates with one of the pair of movable current-carrying contacts 51. Fixed main contacts 11 and 14 cooperate with movable main contacts 21 and 24, respectively, and fixed auxiliary contacts 12 and 13 cooperate with movable auxiliary contacts 22 and 23, respectively. The term cooperate as used in this context with reference to two contacts means that the two contacts may engage each other, as well as disengage from each other. All movable contacts 5l,21,22,23,24,51 are conductively connected to Y-terminal 45.

In the position of parts shown in FIG. 9 contacts 51 and 55 are in engagement, and contacts 21 and 11 are in engagement, and all other contacts are disengaged from one another. The resistance between contacts 21 and 11 exceeds the resistance between contacts 51 and 55. Hence the bulk of the current flowing from tap A to terminal 45 flows via current-carrying contacts 51 and 55. In the position of parts shown in FIG. contact 51 has parted from contact 55, and contact 22 has engaged contact 12. Hence the bulk of the current flowing from tap A to terminal 45 will flow via main contacts 21 and 11. FIG. 11 differs from FIG. 10 in that the former illustrates a point of time when main contacts 21 and 11 have parted. Hence there is but one single current path between tap A and terminal 45, and this current path is highly resistive since it includes resistor W. The next phase in the operation of the transfer switch involves engagement of auxiliary contacts 23 and 13, while auxiliary contacts 22 and 12 remain in engagement. This phase is shown in FIG. 12. In the position of parts shown in FIG. 12 taps A and B are shunted by a current path including auxiliary contacts 12,22, one of the resistors W, terminal 45, the other of resistors W, and auxiliary contacts 23,13. When auxiliary contact 22 parts from auxiliary contact 12, as shown in FIG. 13, only tap B is conductively connected to terminal 45. Thereafter, movable main contact 24 engages fixed main contact 14, thus establishing a direct current path of relatively low resistance between tap B and terminal 45. When the right current-carrying contact 51 engages the right current-carrying contact 55, as shown in FIG. 15, a direct current path of still lower contact resistance is established between tap B and tenninal 45.

The structure of FIGS. 1-8 performs the same switching operations as described above in connection with FIGS. 9-14, except that FIGS. 9-15 show an arrangement wherein a single point of contact is established and a single break formed in each current path of the transfer switch, while FIGS. 1-8 refer to a structure wherein two points of contact are established and double breaks are formed in each current path of the transfer switch. In other words, each fixed contact in the structure of FIGS. 9-15 is replaced in the structure of FIGS. 1-8 by a pair of fixed contacts, and each movable contact in the structure of FIGS. 9-15 is replaced in the structure of FIGS. 1-8 by a pair of movable contacts. The same reference characters have been applied in FIGS. 9-15 to indicate single contacts as have been applied in FIGS. l-8 to indicate corresponding pairs of contacts.

Referring now more particularly to the sequence of steps illustrated in FIGS. 5-8, FIG. 5 illustrates the same position of parts as illustrated in FIG. 9, i.e., current-carrying contacts 51 and 55 are in engagement, and main contacts 21 and 11 are also in engagement, and all other contacts are separated from each other. The helical compression springs 40 interposed between sleeves 30 and slide members 38 are oriented in such directions that their pressure is at right angles to the engaging surfaces of main contacts 11 and 21, thus exerting a maximum of contact pressure. The position of the constituent parts of the structure of FIGS. 1 and 2 shown in FIG. 5 is stable since each contact-operating member 35 has two fixed points defined by fixed main contacts 21 and fixed fulcrum means or rods 42.

In order to effect a tap-changing operation drive shaft 29 and sleeve 30 are pivoted in clockwise direction as seen in FIG. 5. The motion of drive shaft 29 and sleeves 30 is transmitted to each contact-operating segment 35 by the intermediary of pins 39 of fork-shaped, or U-shaped slide member, or spring support 38. Since studs 42 are fixed in space, pins 39 of fork-shaped, or U-shaped spring supports 38 are caused to pivot in counterclockwise direction about studs 42, as clearly shown in FIG. 6. As a result of this motion of contact-operating segments 35, the lattericparate the movable main contacts 21 from their cooperating fixed contacts 11, and cause engagement of fixed auxiliary contacts 12 by movable auxiliary contacts 22. The motion of contact-operating segment 35 is transmitted to movable contacts 21 and 22 by the intermediary of pins, or shafts 41. In the position of the parts of the transfer switch shown in FIG. 6 the direction of the pressure exerted by helical compression springs 40 is at right angles to the contact surfaces of auxiliary contacts 12 and 22, thus maximizing the contact pressure between these contacts.

Continued pivotal motion of shaft 29, sleeves 30, arms 31 and slide members 38 in clockwise direction results in continued counterclockwise pivotal motion of contact-operating segments 35, and of pins 39 about studs 42, as clearly shown in FIG. 7. This counterclockwise pivotal motion of parts 35 and 39 results in engagement of fixed auxiliary contacts 13 by movable auxiliary contacts 23 and in subsequent disengagement of movable auxiliary contacts 22 from fixed auxiliary contacts 12. This position of parts is shown in FIG. 7. The upper left portion of FIG. 2 shows a position of parts preceding the position of parts shown in FIG. 7, namely the position of one contactoperating segment 35 and of two shafts, or studs 41 causing engagement of movable auxiliary contacts 22,23 with fixed auxiliary contacts 12,13. In other words, the position of parts shown in the upper left portion of FIG. 2 corresponds to the position of parts shown in FIG. 12. The position of parts shown in FIG. 7 corresponds to the position of parts shown in FIG. 13, all contacts being out of engagement except auxiliary contacts 13,23. In the position of parts shown in FIG. 7 compression spring 40 exerts a pressure between auxiliary contacts 23 and 13 which is at right angles to the contact surfaces thereof, thus maximizing contact pressure between auxiliary contacts 23 and 13.

FIG. 8 shows drive shaft 19, sleeve 30 and segment 35 in their limit positions which correspond to the position of parts shown in FIG. 15. Both FIG. 8 and 15 show the movable main contacts 24 in engagement with the fixed main contacts 14, and the adjacent movable current-carrying contacts 51 in engagement with the fixed current-carrying contacts 55, all other contacts being out of engagement. The transient position between that shown in FIG. 7 and that shown in FIG. 8 is diagrammatically illustrated in FIG. 14 showing auxiliary contacts 23 and 13 to be in engagement, and main contacts 24 and 14 to be in engagement, all other contacts being disengaged. Pivotal movement of contact-operating segment 35 about fulcrum means, or stud 42 in counterclockwise direction results in separation of auxiliary contacts 23 and 13, and engagement of current-carrying contacts 51 and 55, while main contacts 24 and 14 remain in engagement. In the limit position of FIG. 8 the direction of the action of compression spring 40 is at right angles to the contact surfaces of engaging main contacts 24 and 14.

It will be apparent from the above and particularly from viewing FIGS. -8 that the motion of contact-operating segments 35 is not a simple pivotal motion about fixed fulcrum means or studs 42, but a composite motion involving radial displacements of contact-operating segments 35 toward and away from cylindrical contact support 10. These radial displacements are made possible by the median guide means, or slots 37 in contact-operating segments 35, and by the radially extending straight slots 32 in arms 31 of sleeve 30. The above composite movement of contact-operating segments 35 is particularly evident when considering the relative position of fixed rods 42 in slots 37 during a full duty cycle, i.e., during the transition from the limit position shown in FIG. 5 to the limit position shown in FIG. 8. It is also apparent from FIGS. 5 to 8 that the distance of contact-operating segments 35 from fixed contacts 55,11,12 is relatively small, and the distance of contact-operating segments 35 from fixed contacts 55,14,13 relatively large at the beginning of the strike of the transfer switch, while the distance of contact-operating segments 35 from fixed contacts 55,11,12 is relatively large, and the distance of contact-operating segments 35 from fixed contacts 55,14,13 relatively small at the end of the stroke of the transfer switch.

The above desired switching mechanism makes it possible to achieve readily relatively large separations between parting contacts. This, in turn, tends to minimize the danger of restrikes, or reignitions.

The contact-operating segments 35 may be formed by simple parts of a synthetic resin, or plastic. They replace functionally the relatively complicated linkages which were generally used heretofore to perform the above described transfer switch operations. This simplicity greatly reduces manufacturing cost as well as the cost of maintenance. The contact velocities may readily be optimized by imparting the proper proportions to the lateral guide means, or slots 36 controlling the movements of the movable contacts 21,22,23,24, thus making it possible to contact the rate of rise of the arc voltage and to minimize the are energy involved in switching operations.

It will be understood that slots 36 and 37 are, in effect, a particular form of cam means integral with contact-operating members 35, slots 36 being a cam means for operating contact supports of movable contacts 21-24 in accordance with a desired travel versus time characteristic, and slots 37 being a cam means for imparting a desired composite pivotal and linear motion to each of the contact-operating members 35. While these ends may be achieved by guide means, or cam means, other than the slots 36 and 37 in member 35, slots 36 and 37 in member 35 are preferred means for achieving these ends. Pins, or studs 42 projecting through slots 37 are arranged in the median plane of the pattern formed by fixed contacts ll,12,l3,14 at points situated between said circular pattern and its center, or hollow shaft 19, respectively.

A tap-changing operation from tap B of FIG. 9 to tap A of FIG. 9 is the reverse of that illustrated in FIGS. 9-15 and described in connection with these figures and in connection with FIGS. 5-8. Therefore such a tap-changing operation, i.e., the constituent steps, or phases thereof, are self-evident and do not call for a detailed description.

It is further apparent from the above that a transfer switch embodying this invention includes three groups of fixed contacts ll,12,13,14. Each plurality of fixed contacts 11-14 is arranged in a sector-of-a-circle pattern. l-Iollow drive shaft 19 is arranged in the center of said sector-of-a-circle pattern.

Sleeve 30, slotted arms 31, slide members 38 and pins 39 are torque-transmitting means for transmitting torques from hollow drive shaft 39 to contact-operating members 35. The slots 32 in arms 31 engaged by slide members 38 are means provided to allow radial movements of members 35 relative to shaft 29 while the aforementioned torque-transmitting means transmit torques from shaft 29 to contact-operating members 35.

The slots 26 in plates 27 sandwiching contact-operating members 35 are guide means confining the trajectories ofcontact supports 25 and of movable contacts 2I,21;22,22;23,23 and 24,24 supported by contact supports 25 to straight radially extending lines each interconnecting the aforementioned center of a sector-of-a-circle pattern with one of the plurality offixed contacts 11,12,l3,l4.

The directions of the straight components of the motions performed by contact-operating member 35 are determined at any point of time by the lines of intersection of median guide means, or slots 37 of contact-operating members 35 and fixed fulcrum means, or studs 42.

Drive shaft 29 is arranged in the center of the circular pattern formed by fixed contacts 21,22,23,24. Drive shaft 29 is pivotable between a pair of limit positions of which each is determined by the radial alignment of shaft 29, one of the pair of fixed outer main contacts 21 and 24, respectively, and one of the radially outer movable main contact operating pin means 41.

It will be apparent from FIG. 3 that the flange portions of slide members 38 supporting pivots 39 sandwich the radially inner ends of contact-operating members 35 and that the spacing between said flange portions is about equal to the thickness of contact-operating member 35 It will be understood that the transfer switch which has been disclosed is a preferred embodiment of our invention, and that the same may be embodied in various structures differing more or less from our preferred embodiment.

We claim as our invention:

1. A transfer switch for tap-changing regulating transformers including:

a. a plurality of fixed contacts (1l,12,l3,14) arranged in a sector-of-a-circle pattern;

b. a plurality of movable contacts (21,22,23,24) each movable into and out of engagement with one of said plurality offixed contacts (1l,l2,13,14);

. a fixed contact guide structure (27,26) for guiding said plurality of movable contacts (21,22,23,24) along radial trajectories each extending from the center of said sectorof-a-circle pattern toward one of said plurality of fixed contacts (1 l,12,13,14);

d. a movable contact-operating member (35) for operating said plurality of movable contacts (1l,l2,l3,14) having a substantially straight center guide means (37) arranged in the median plane of said contact-operating member (35) and cooperating with a fixed fulcrum means (42) to allow said contact-operating member (35 to pivot about said fixed fulcrum means (42) and to move simultaneously radially relative to the center of said sector-of-a-circle pattern, said contact-operating member (35 being further provided with a pair of lateral arcuate guide means (36) arranged to opposite sides of said center guide means (37) thereof;

e. a plurality of operating pin means (41) each operatively related to one of said plurality of movable contacts (21,22,23,24) and each under the control of one of said pair of lateral arcuate guide means (36) to impart motions of said contact-operating member (35) to said plurality of movable contacts (21,22,23,24);

f. a pivotable drive shaft (29) for operating said contactoperating member (35) arranged in the center of said sector-of-a-circle pattern at right angles to a plane defined by said plurality of fixed contacts (l1,12,13,14);

g. spring means (40) biasing said contact-operating (35) member radially outwardly away from said drive shaft (29); and

h. torque-transmitting means (30,3l,38,39) for transmitting torques from said drive shaft (29) to said contact-operating member (35) adapted to allow radial movements of said contact-operating member (35) relative to said drive shaft (29).

2. A transfer switch as specified in claim 1 wherein a. said plurality of fixed contacts is supported by a hollow cylindrical fixed contact support (10) of insulating material and arranged on the inner surface of said support; wherein b. said fixed contact guide structure includes plate means (27) arranged at right angles to said drive shaft (29) and provided with radial slots (26) defining said radial trajec tories; wherein c. said spring means (40) is a compression spring arranged between said drive shaft (29) and said contact-operating member (35); and wherein d. said torque-transmitting means include a torque-transmitting pin (39) arranged parallel to and spaced from said drive shaft (29) and means (32) defining a slot allowing variations of the spacing between said drive shaft (29) and said torque-transmitting pin (39).

3 A transfer switch as specified in claim 1 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29) and wherein said center guide means (37) of said contact-operating member (35) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by cam surfaces integral with said contact-operating member (35).

4. A transfer switch as specified in claim 1 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29), wherein said center guide means (37) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by slots extending from one end surface of said contact-operating member to the other end surface thereof, and wherein said fixed fulcrum means (42) is formed by a rod projecting transversely through the slot forming said center guide means (37) of said contact-operating member (35) and beyond the end surfaces of said contact-operating member (35).

5. A transfer switch as specified in claim 1 wherein a. said fixed contact guide structure is formed by a pair of spaced guide plates (27) of insulating material arranged at right angles to said drive shaft (29), said pair of guide plates (27 being provided with radial slots (26) defining said radial trajectories of said plurality of movable contacts (21,22,23,24); wherein b. said contact-operating member (35 is in the shape of a contact-operating plate arranged at right angles to said drive shaft (29) and in the space between said pair of guide plates (27), said center guide means (37) and said pair of lateral arcuate guide means (36) being formed by slots extending through said contact-operating plate (35) from one end surface to the other end surface thereof: wherein c. said fixed fulcrum means (42) is formed by a rod projecting transversely through the slot forming said center guide means (37) of said contact-operating plate (35) and beyond the end surfaces thereof; and wherein d. said plurality of operating pin means (41) project transversely through the slots forming said pair of lateral arcuate guide means (36) of said contact-operating plate (35) and beyond the end surfaces thereof and through said radial slots (26) in said pair of guide plates (27).

6. A transfer switch as specified in claim 1 wherein said torque-transmitting means include a pair of arms (31) jointly pivotable with said drive shaft (29) and projecting radially outwardly from said drive shaft (29) and defining a pair of axially spaced radially extending slots (32), a substantially U- shaped spring support (38) having flange portions guided in said slots (32) and a web portion, helical spring means (40) being interposed between said drive shaft (29) and said web portion of said spring support (38) to bias said spring support (38) radially outwardly from said drive shaft (29), and a pin (39) projecting transversely through said flange portions of said spring support (38) radially outwardly from said drive shaft (29), and a pin (39) projecting transversely through said flange portions of said spring support (38) and through the radially inner end of said contact-operating member (35).

7. A transfer switch as specified in claim 1 wherein a. said plurality of fixed contacts is supported by a cylindrical hollow contact support (10) of insulating material on the inner surface of said support; wherein b. said fulcrum means is formed by a fixed rod arranged parallel to said drive shaft (29); wherein c. said straight center guide means (37) of said contactoperating member (35) is formed by a slot allowing said fixed rod to project transversely through said contactoperating member (35); wherein (1. said cylindrical contact support (10) supports an insulating structure (43) having a pair of axially spaced arms extending radially inwardly from said cylindrical contact support (10) and sandwiching said contact-operating member (35) therebetween, said pair of arms of said insulating structure (43) supporting the axially outer ends of said fixed rod; wherein e. aid fixed guide structure is formed by a pair of spaced plates (27) of insulating material arranged at right angles to said drive shaft (29) and having radially outer ends affixed to said pair of arms of said insulating structure (43), and wherein f. said insulating structure (43) supports terminal element means (45) arranged outside of said cylindrical contact support (10).

8. A transfer switch as specified in claim 7 wherein said cylindrical contact support (10) is provided with a cutout, and wherein said insulating structure (43) projects radially outwardly through said cutout and defines a recess in the radially outer portion thereof receiving said terminal element means (45).

9. A transfer switch as specified in claim 1 including a plurality of arc-chutes (34) each for one of said plurality of fixed contacts (ll,l2,13,l4) and one of said plurality of movable contacts (21,22,23,24), each of said plurality of arc-chutes (34) extending radially inwardly from said cylindrical contact support (10) and being arranged in alignment with one of said radial trajectories of said plurality of movable contacts (2l,22,23,24).

10. A transfer switch as specified in claim 1 wherein; said contact-operating member (.35) supports pivotally at opposite sides of said straight center guide means (37) thereof substan tially bellcrank-shaped spring-biased movable current-carrying contacts (51) arranged to engage cooperating fixed current-carrying contacts (55).

11. A transfer switch as specified in claim 10 wherein the contact surfaces of said fixed current-carrying contacts (55) and the contact surfaces of said movable current-carrying contacts (51) are arrangedin such a direction that the spring bias of said movable current-carrying contacts (51) is substantially atright angles to the engaging contact surfaces of said fixed current-carrying contacts (55) and of said movable current-carrying contacts (51 12. A transfer switch for tap-changing regulating transformers including:

a. a plurality of fixed contacts (ll,l2,l3,l4) arranged in a sectorof-a'circle pattern and including a pair of fixed outer main contacts (11,14) and fixed inner auxiliary contacts (12,13);

b. a fixed fulcrum means (42) arranged in the median plane of said sector-of-a-circle pattern at a point situated between said sector-of-a-circle pattern and the center of said sector-of-a-circle pattern;

. a movable contact-operating member (35) having substantially straight median guide means (37) cooperating with said fixed fulcrum means (42) to allow said contactoperating member (35) to perform composite motions including a circular component with said fixed fulcrum means (42) as center and a substantially straight component in a direction determined at any point of time by the line of intersection of said median guide means (37 of said contact-operating member (35) and said fixed fulcrum means (2), said contact-operating member (35 being further provided with a pair of lateral arcuate guide means (36) arranged to opposite sides of said median guide means (37);

d. a plurality of movable contacts (21,22,23,24) cooperating with said plurality of fixed contacts (11,12,13,14) and including a pair of movable outer main contacts (21,24) and movable inner auxiliary contacts (22,23), said plurality of movable contacts (21,22,23,24) being provided with guide means (26,27) confining the trajectories thereof to straight radially extending lines each interconnecting said center of a sector-of-a-circle pattern with one of said plurality of fixed contacts (1 1,12,13,14);

'e. a plurality of pin means (41) each operatively related to one of said plurality of movable contacts (21,22,23,24) and each engaging one of said pair of lateral arcuate guide means (36) of said contact-operating member (35) to transmit motions of said contact-operating member (35) to said plurality of movable contacts (21,22,23,24), said plurality of pin means (41) including a pair of outer movable main contact-operating pin means (41);

. compression spring means (40) having a radially inner end arranged adjacent said center of said sector-of-a-circle pattern and a radially outer end applying a radial force against said contact-operating member (35) tending to move said contact-operating member (35) radially outwardly away from said center of said sector-of-a-circle pattern;

g. a drive shaft (29) arranged in said center of said sectorof-a-circle pattern and pivotable between a pair of limit positions each determined by the radial alignment of said center of said sector-of-a circle pattern, one of said pair of fixed outer main contacts (11,12,13,14) and one of said pair of outer movable main contact-operating pin means (41); and

h. torque-transmitting means (30,3l,38,39) for transmitting torques from said drive shaft (29) to said contact-operating member (35) and to thereby effect pivotal motions of said contact-operating member (35 about said fulcrum means (42) in a direction opposite to the pivotal motion of said drive shaft (29), said torque-transmitting means including means (32) allowing radial movements of said contact-operating member (35) relative to said drive shaft (29).

13. A transfer switch as specified in claim 12 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29) and wherein said median guide means (37) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by cam surfaces integral with said contactoperating member (35).

14. A transfer switch as specified in claim 12 wherein said contact-operating member (35 is substantially in the shape of a plate arranged at right angles to said drive shaft (29), and wherein said median guide means (37) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by slots extending from one end surface of said contact-operating member (35 to the other end surface thereof.

15. A transfer switch as specified in claim 12 wherein said guide means confining the trajectories of said plurality of movable contacts (21,22,23,24) to straight radially extending lines include a pair of spaced-parallel plates (27) of insulating material arranged at right angles to said drive shaft (29), sandwiching said contact-operating member (35), and having radially extending slots (26) each engaged by one of said plurality ofpin means (41).

16. A transfer switch as specified in claim 12 including a. a hollow drive shaft (29);

b. arm means (31) jointly pivotable with said hollow drive shaft (29) and extending radially outwardly from said hollow drive shaft (29);

c. a slide member (38) movable relative to said arm means (31) in a direction longitudinally thereof, said radially outer end of said compression spring means (40) resting against said slide member (38) and biasing said slide member (38) radially outwardly away from said hollow drive shaft (29 and I d. pin means (3 pivotally connecting said slide member (38) to said contact-operating member (35) and allowing pivotal motions of said contact-operating member (35) relative to said slide member (38).

17. A transfer switch as specified in claim 12 including a. a hollow drive shaft (29);

b. a sleeve (30) fixedly mounted on said hollow drive shaft for joint pivotable motion with said hollow drive shaft c. a pair of axially spaced arm means (31) integral with said sleeve (30) extending radially outwardly from said sleeve (30) and each having a straight slot (32) extending in a direction longitudinally of said pair of arm means (31);

d. a U-shaped slide member (38) having a pair of flange portions sandwiching said contact-operating member (35) each arranged inside of and guided by said slot (32) in one of said pair of arm means (31) and a web portion, said compression spring means (40) being interposed between said sleeve (30) and said slide member (38) and biasing said slide member (38) radially outwardly away from said sleeve (30); and

. pin means (39) projecting at right angles through said pair of flange portions of said slide member (38) and said contact-operating member (35) pivotally connecting said contact-operating member (35) to said slide member (38) and allowing pivotal motions of said contact-operating member (35) relative to said slide member (38).

18. A transfer switch as specified in claim 12 including a. a pair of pivots (52) supported by said contact-operating member (35) and arranged to opposite sides of said median guide means (37) thereof;

b. bellcrank-shaped movable current-carrying contacts (51) each having a pair of arms and each being pivotally supported on said contact-operating member (35) by means of one of said pair of pivots (52) at a point situated between said pair of arms, one of said pair of arms of each of said current-carrying contacts (51) forming a contact surface;

0. spring means (53) acting upon the other of said pair of arms of said movable current-carrying contacts (51) and biasing said current-carrying contacts (51) in opposite senses; and

. fixed current-carrying contacts (55) arranged to be engaged by said contact surface of one of said pair of arms of said movable current-carrying contacts (51). 

1. A transfer switch for tap-changing regulating transformers including: a. a plurality of fixed contacts (11,12,13,14) arranged in a sector-of-a-circle pattern; b. a plurality of movable contacts (21,22,23,24) each movable into and out of engagement with one of said plurality of fixed contacts (11,12,13,14); c. a fixed contact guide structure (27,26) for guiding said plurality of movable contacts (21,22,23,24) along radial trajectories each extending from the center of said sector-ofa-circle pattern toward one of said plurality of fixed contacts (11,12,13,14); d. a movable contact-operating member (35) for operating said plurality of movable contacts (11,12,13,14) having a substantially straight center guide means (37) arranged in the median plane of said contact-operating member (35) and cooperating with a fixed fulcrum means (42) to allow said contact-operating member (35) to pivot about said fixed fulcrum means (42) and to move simultaneously radially relative to the center of said sector-of-a-circle pattern, said contactoperating member (35) being further provided with a pair of lateral arcuate guide means (36) arranged to opposite sides of said center guide means (37) thereof; e. a plurality of operating pin means (41) each operatively related to one of said plurality of movable contacts (21,22,23,24) and each under the control of one of said pair of lateral arcuate guide means (36) to impart motions of said contact-operating member (35) to said plurality of movable contacts (21,22,23,24); f. a pivotable drive shaft (29) for operating said contactoperating member (35) arranged in the center of said sector-ofa-circle pattern at right angles to a plane defined by said plurality of fixed contacts (11,12,13,14); g. spring means (40) biasing said contact-operating (35) member radially outwardly away from said drive shaft (29); and h. torque-transmitting means (30,31,38,39) for transmitting torques from said drive shaft (29) to said contact-operating member (35) adapted to allow radial movements of said contactoperating member (35) relative to said drive shaft (29).
 2. A transfer switch as specified in claim 1 wherein a. said plurality of fixed contacts is supported by a hollow cylindrical fixed contact support (10) of insulating material and arranged on the inner surface of said support; wherein b. said fixed contact guide structure includes plate means (27) arranged at right angles to said drive shaft (29) and provided with radial slots (26) defining said radial trajectories; wherein c. said spring means (40) is a compression spring arranged between said drive shaft (29) and said contact-operating member (35); and wherein d. said torque-transmitting means include a torque-transmitting pin (39) arranged parallel to and spaced from said drive shaft (29) and means (32) defining a slot allowing variations of the spacing between said drive shaft (29) and said torque-transmitting pin (39).
 3. A transfer switch as specified in claim 1 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29) and wherein said center guide means (37) of said contact-operating member (35) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by cam surfaces integral with said contact-operating member (35).
 4. A transfer switch as specified in claim 1 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29), wherein said center guide means (37) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by slots extending from one end surface of said contact-operating member to the other end surface thereof, and wherein said fixed fulcrum means (42) is formed by a rod projecting transversely through the slot forming said center guide means (37) of said contact-operating member (35) and beyond the end surfaces of said contact-operating member (35).
 5. A transfer switch as specified in claim 1 wherein a. said fixed contact guide structure is formed by a pair of spaced guide plates (27) of insulating material arranged at right angles to said drive shaft (29), said pair of guide plates (27) being provided with radial slots (26) defining said radial trajectories of said plurality of movable contacts (21, 22,23,24); wherein b. said contact-operating member (35) is in the shape of a contact-operating plate arranged at right angles to said drive shaft (29) and in the space between said pair of guide plates (27), said center guide means (37) and said pair of lateral arcuate guide means (36) being formed by slots extending through said contact-operating plate (35) from one end surface to the other end surface thereof: wherein c. said fixed fulcrum means (42) is formed by a rod projecting transversely through the slot forming said center guide means (37) of said contact-operating plate (35) and beyond the end surfaces thereof; and wherein d. said plurality of operating pin means (41) project transversely through the slots forming said pair of lateral arcuate guide means (36) of said contact-operating plate (35) and beyond the end surfaces thereof and through said radial slots (26) in said pair of guide plates (27).
 6. A transfer switch as specified in claim 1 wherein said torque-transmitting means include a pair of arms (31) jointly pivotable with said drive shaft (29) and projecting radially outwardly from said drive shaft (29) and defining a pair of axially spaced radially extending slots (32), a substantially U-shaped spring support (38) having flange portions guided in said slots (32) and a web portion, helical spring means (40) being interposed between said drive shaft (29) and said web portion of said spring support (38) to bias said spring support (38) radially outwardly from said drive shaft (29), and a pin (39) projecting transversely through said flange portions of said spring support (38) radially outwardly from said drive shaft (29), and a pin (39) projecting transversely through said flange portions of said spring support (38) and through the radially inner end of said contact-operating member (35).
 7. A transfer switch as specified in claim 1 wherein a. said plurality of fixed contacts is supported by a cylindrical hollow contact support (10) of insulating material on the inner surface of said support; wherein b. said fulcrum means is formed by a fixed rod arranged parallel to said drive shaft (29); wherein c. said straight center guide means (37) of said contact-operating member (35) is formed by a slot allowing said fixed rod to project transversely through said contact-operating member (35); wherein d. said cylindrical contact support (10) supports an insulating structure (43) having a pair of axially spaced arms extending radially inwardly from said cylindrical contact support (10) and sandwiching said contact-operating member (35) therebetween, said pair of arms of said insulating structure (43) supporting the axially outer ends of said fixed rod; wherein e. said fixed guide structure is formed by a pair of spaced plates (27) of insulating material arranged at right angles to said drive shaft (29) and having radially outer ends affixed to said pair of arms of said insulating structure (43), and wherein f. said insulating structure (43) supports terminal element means (45) arranged outside of said cylindrical contact support (10).
 8. A transfer switch as specified in claim 7 wherein said cylindrical contact support (10) is provided with a cutout, and wherein said insulating structure (43) projects radially outwardly through said cutout anD defines a recess in the radially outer portion thereof receiving said terminal element means (45).
 9. A transfer switch as specified in claim 1 including a plurality of arc-chutes (34) each for one of said plurality of fixed contacts (11,12,13,14) and one of said plurality of movable contacts (21,22,23,24), each of said plurality of arc-chutes (34) extending radially inwardly from said cylindrical contact support (10) and being arranged in alignment with one of said radial trajectories of said plurality of movable contacts (21,22,23,24).
 10. A transfer switch as specified in claim 1 wherein said contact-operating member (35) supports pivotally at opposite sides of said straight center guide means (37) thereof substantially bellcrank-shaped spring-biased movable current-carrying contacts (51) arranged to engage cooperating fixed current-carrying contacts (55).
 11. A transfer switch as specified in claim 10 wherein the contact surfaces of said fixed current-carrying contacts (55) and the contact surfaces of said movable current-carrying contacts (51) are arranged in such a direction that the spring bias of said movable current-carrying contacts (51) is substantially at right angles to the engaging contact surfaces of said fixed current-carrying contacts (55) and of said movable current-carrying contacts (51).
 12. A transfer switch for tap-changing regulating transformers including: a. a plurality of fixed contacts (11,12,13,14) arranged in a sector-of-a-circle pattern and including a pair of fixed outer main contacts (11,14) and fixed inner auxiliary contacts (12, 13); b. a fixed fulcrum means (42) arranged in the median plane of said sector-of-a-circle pattern at a point situated between said sector-of-a-circle pattern and the center of said sector-of-a-circle pattern; c. a movable contact-operating member (35) having substantially straight median guide means (37) cooperating with said fixed fulcrum means (42) to allow said contact-operating member (35) to perform composite motions including a circular component with said fixed fulcrum means (42) as center and a substantially straight component in a direction determined at any point of time by the line of intersection of said median guide means (37) of said contact-operating member (35) and said fixed fulcrum means (2), said contact-operating member (35) being further provided with a pair of lateral arcuate guide means (36) arranged to opposite sides of said median guide means (37); d. a plurality of movable contacts (21,22,23,24) cooperating with said plurality of fixed contacts (11,12,13,14) and including a pair of movable outer main contacts (21,24) and movable inner auxiliary contacts (22,23), said plurality of movable contacts (21,22,23,24) being provided with guide means (26,27) confining the trajectories thereof to straight radially extending lines each interconnecting said center of a sector-of-a-circle pattern with one of said plurality of fixed contacts (11,12,13,14); e. a plurality of pin means (41) each operatively related to one of said plurality of movable contacts (21,22,23,24) and each engaging one of said pair of lateral arcuate guide means (36) of said contact-operating member (35) to transmit motions of said contact-operating member (35) to said plurality of movable contacts (21,22,23,24), said plurality of pin means (41) including a pair of outer movable main contact-operating pin means (41); f. compression spring means (40) having a radially inner end arranged adjacent said center of said sector-of-a-circle pattern and a radially outer end applying a radial force against said contact-operating member (35) tending to move said contact-operating member (35) radially outwardly away from said center of said sector-of-a-circle pattern; g. a drive shaft (29) arranged in said center of said sector-of-a-circle pattern and pivotable between a pair of limit positions each determined by the radial alignment of said center of said sector-of-a-circle pattern, one of said pair oF fixed outer main contacts (11,12,13,14) and one of said pair of outer movable main contact-operating pin means (41); and h. torque-transmitting means (30,31,38,39) for transmitting torques from said drive shaft (29) to said contact-operating member (35) and to thereby effect pivotal motions of said contact-operating member (35) about said fulcrum means (42) in a direction opposite to the pivotal motion of said drive shaft (29), said torque-transmitting means including means (32) allowing radial movements of said contact-operating member (35) relative to said drive shaft (29).
 13. A transfer switch as specified in claim 12 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29) and wherein said median guide means (37) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by cam surfaces integral with said contact-operating member (35).
 14. A transfer switch as specified in claim 12 wherein said contact-operating member (35) is substantially in the shape of a plate arranged at right angles to said drive shaft (29), and wherein said median guide means (37) and said pair of lateral arcuate guide means (36) of said contact-operating member (35) are formed by slots extending from one end surface of said contact-operating member (35) to the other end surface thereof.
 15. A transfer switch as specified in claim 12 wherein said guide means confining the trajectories of said plurality of movable contacts (21,22,23,24) to straight radially extending lines include a pair of spaced-parallel plates (27) of insulating material arranged at right angles to said drive shaft (29), sandwiching said contact-operating member (35), and having radially extending slots (26) each engaged by one of said plurality of pin means (41).
 16. A transfer switch as specified in claim 12 including a. a hollow drive shaft (29); b. arm means (31) jointly pivotable with said hollow drive shaft (29) and extending radially outwardly from said hollow drive shaft (29); c. a slide member (38) movable relative to said arm means (31) in a direction longitudinally thereof, said radially outer end of said compression spring means (40) resting against said slide member (38) and biasing said slide member (38) radially outwardly away from said hollow drive shaft (29); and d. pin means (39) pivotally connecting said slide member (38) to said contact-operating member (35) and allowing pivotal motions of said contact-operating member (35) relative to said slide member (38).
 17. A transfer switch as specified in claim 12 including a. a hollow drive shaft (29); b. a sleeve (30) fixedly mounted on said hollow drive shaft for joint pivotable motion with said hollow drive shaft (29); c. a pair of axially spaced arm means (31) integral with said sleeve (30) extending radially outwardly from said sleeve (30) and each having a straight slot (32) extending in a direction longitudinally of said pair of arm means (31); d. a U-shaped slide member (38) having a pair of flange portions sandwiching said contact-operating member (35) each arranged inside of and guided by said slot (32) in one of said pair of arm means (31) and a web portion, said compression spring means (40) being interposed between said sleeve (30) and said slide member (38) and biasing said slide member (38) radially outwardly away from said sleeve (30); and e. pin means (39) projecting at right angles through said pair of flange portions of said slide member (38) and said contact-operating member (35) pivotally connecting said contact-operating member (35) to said slide member (38) and allowing pivotal motions of said contact-operating member (35) relative to said slide member (38).
 18. A transfer switch as specified in claim 12 including a. a pair of pivots (52) supported by said contact-operating member (35) and arranged to opposite sides of said median guide means (37) thereof; b. bellcrank-shaped movable current-carrying contacts (51) each having a pair of arms and each being pivotally supported on said contact-operating member (35) by means of one of said pair of pivots (52) at a point situated between said pair of arms, one of said pair of arms of each of said current-carrying contacts (51) forming a contact surface; c. spring means (53) acting upon the other of said pair of arms of said movable current-carrying contacts (51) and biasing said current-carrying contacts (51) in opposite senses; and d. fixed current-carrying contacts (55) arranged to be engaged by said contact surface of one of said pair of arms of said movable current-carrying contacts (51). 